The invention relates to an apparatus for the monitored metering of NO into the respiratory air and analysis of the inspiratory and expiratory air of patients with, for example, ARDS or similar syndromes.
ARDS (adult respiratory distress syndrome) is a serious failure of the lungs of adults in which a persistent serious disturbance of gas exchange in the lungs is accompanied by an elevated blood pressure in the pulmonary circulation. This elevated pressure leads to a serious stress on the right heart and consequently to right heart failure. Apart from ARDS, elevated pressure in the pulmonary circulation may also occur in preterm infants and associated with certain cardiac malformations. It is possible per se to reduce the elevated pressure in the pulmonary circulation by administering agents which lower blood pressure. However, these act on the entire blood circulation. Since, as a rule, the blood pressure is already too low in patients with ARDS, it is therefore possible to administer such agents which lower blood pressure only with great restrictions.
It has been known for some years that a specific reduction in the elevated pressure in the pulmonary circulation is possible by metering NO (nitric oxide) into patients' respiratory air. The NO has a vasodilating effect and, as a consequence of the enlargement of the cross-section of vessels, leads to a reduction in the blood pressure in the pulmonary circulation. The difficulties arising in treatment with NO are that fault-free treatment with NO must be ensured over a period of several weeks. Another difficulty which may arise is that toxic NO.sub.2 (nitrogen dioxide ) may be formed from part of the NO in the patient's lung.